Dogs can eat banana bread only if it is plain and free from toxic ingredients such as chocolate, walnuts, raisins, or xylitol. While the basic ingredients of banana bread (bananas, flour, sugar, eggs) are not toxic, banana bread is generally not a healthy treat for dogs due to its high sugar and fat content. Small portions of plain banana bread are unlikely to harm a healthy dog, but it's better to avoid feeding it regularly, especially for dogs with health conditions like diabetes or obesity. Always check the ingredients carefully, and consult your vet if unsure.